The present invention relates to an automatic sawmill and particularly to automatic sawmill method and apparatus for removing an irregular edge from a cant or board.
In automatic sawmill operation, a maximum recovery in board feet of lumber from incoming logs is desired, as well as high volume capacity for handling and cutting the maximum lumber in a given period of time. One problem associated with automatic sawmill operation is removal of the irregular lateral edge on a plank or a cant. For example, it is necessary to remove the wane edge on a plank or cant, i.e. the rounded or non-squared edge resulting when such plank or cant is sawn lengthways from a round log. The wane must be removed, within certain tolerance restrictions, before the plank or cant is processed into dimensioned lumber. Of course, the wane can be sawn from the cant after visual inspection or measurement by operating personnel, but this can be unnecessarily expensive and time consuming. Merely trimming all cants within certain dimensions to remove all possible wane areas would be unduly wasteful.
Automatic detectors for measuring uneven edges or wanes are known, but implementing the measurements derived therefrom for removing the undesired irregular edge or wane may be somewhat inaccurate. Again, the wane may then be removed essentially by rough estimation, or prescribing a saw line which is sufficiently inside the edge of the cant to remove all irregularities therefrom. Of course, this still would result in waste. It is also possible to select one or more points along the wane, e.g. substantially separated points, or the most deeply indented wane points and merely saw the wane through such points. However, this method frequently produces unacceptable boards when a part of the irregular edge is not removed. Any arbitrarily determined saw cut may leave unacceptable wane portions on the board, and will not consistently produce the optimum lumber output.